This invention relates to a display device for use in constructing bulletin boards and the like. More particularly, the invention relates to a display device in which the display element consists of a disc which has separate surfaces which are differently colored and which can be flipped about its supporting axis by remote control so as to display a surface having a selected color.
Remote control alphanumeric display devices are currently in use, for example, in bulletin boards at airports, in highway signs, and in bus signs where a multiplicity of discs are arranged in a plurality of rows, each disc being pivotably mounted so that one or the other of the contrastingly colored sides of each disc is exposed to view. By selecting the sides which are displayed, alphanumeric characters are formed which convey a message to the viewer. The discs may be circular, triangular, quadrilateral, or polygonal in shape.
In the known devices, a magnetically polarized element which forms part of a pivotable disc structure responds to the presence of the field of an electromagnet which has one magnetic polarity or the other to turn the disc to display one side or the other. The driven permanent magnet may be a polarized magnetic cylinder which is carried adjacent to the disc on the axis on which the disc rotates or it may consist of a permanent magnet which is sandwiched between the surfaces of the disc. In such devices, the development of sufficient motive power to turn an array of display discs about their respective axes requires a series of large electric pulses, using as much as three watts per pulse per coil. An array of such devices generates a substantial amount of heat and has a substantial weight which requires special support to withstand the shocks experienced, for example, in bus displays. Further, at least in versions of these structures having discs which are one-half inch in diameter and larger, the response of the display element is not as fast as would be liked for use in displays where rapidly moving images are to be produced. In versions using discs of less than one-half inch in diameter, activation of one disc can result in undesirable actuation of a neighboring disc.